# How long would it take to stop the 747, as in the Tenet?

This acceleration is for any change in speed. It doesn’t matter if the speed is increasing or decreasing – it’s still acceleration. If you know the acceleration of an object, you can find the stopping distance using the following kinematic equation (Here is a derivation if you want it).

In this expression, v1 Are the starting speed (20 mph in this calculation) and v2 The final velocity will be – hopefully zero because it will stop. Therefore, with known acceleration, the stopping distance (Δx) will be:

Now I just need to get value for acceleration stops a Boeing 747. Ah ha! This is not that easy. Of course, big planes stop all the time – this is commonly called “landing”. However, the normal method during landing will not work here. A large plane like a Boeing 747 usually uses two things to slow it down. Not only does it use wheels that have brakes, they also have reversible drives. Reverse thrusters are basically the power from motors directed backwards (hence the “reverse” part). Rear thrust, combined with the brakes, slows the plane down.

For this trick in Tenet, The 747 will only have brakes because it is not a fully functional aircraft. So, what is acceleration if the plane does not use reverse thrusters? Well, we’re in luck. This thing is called a rejected take-off test (RTO). In this maneuver, the plane takes off and rises to take off quickly. At this point, the pilot applies the brakes (no reverse thrust engines) and stops. It’s a worst-case scenario test to ensure that an aircraft’s brakes can handle the extreme.

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